Structure and types of neurons- Resting membrane potential, action potential, impulse transmission through myelinated and unmyelinated nerve fibres?

Structure and Types of Neurons:
Neurons are the basic building blocks of the nervous system. They are specialized cells that transmit information in the form of electrical signals. Neurons consist of three main parts: the cell body (soma), dendrites, and axon.

1. Cell Body (Soma): The cell body contains the nucleus and other organelles necessary for the neuron's functioning.

2. Dendrites: Dendrites are branched extensions that receive signals from other neurons or sensory receptors. They play a crucial role in integrating incoming information.

3. Axon: The axon is a long, slender projection that carries electrical signals away from the cell body. It is covered by a myelin sheath (in myelinated neurons) or lacks myelin (in unmyelinated neurons).

Types of Neurons:
1. Sensory Neurons: These neurons transmit sensory information from sensory receptors (e.g., in the skin, eyes, ears) to the central nervous system (CNS).

2. Motor Neurons: Motor neurons transmit signals from the CNS to muscles or glands, enabling movement or secretion.

3. Interneurons: Interneurons are found within the CNS and facilitate communication between sensory and motor neurons. They play a crucial role in information processing and integration.

Resting Membrane Potential:
Resting membrane potential refers to the electrical charge difference across the neuronal membrane when the neuron is at rest. It is typically around -70 millivolts (mV) inside the neuron compared to the outside. This potential is maintained by the selective permeability of the neuronal membrane to ions, such as potassium (K+) and sodium (Na+), and the action of ion channels and pumps.

Action Potential:
An action potential is a brief, rapid change in the electrical potential of a neuron. It occurs when a neuron receives a strong enough stimulus, causing the membrane potential to depolarize. This depolarization triggers the opening of voltage-gated sodium channels, allowing an influx of sodium ions into the neuron. This influx generates an electrical impulse that travels down the axon.

Impulse Transmission through Myelinated and Unmyelinated Nerve Fibers:
Myelinated Nerve Fibers: In myelinated neurons, the axon is covered by a fatty substance called myelin, which is produced by specialized cells called oligodendrocytes in the CNS and Schwann cells in the peripheral nervous system (PNS). The myelin sheath acts as an insulator, preventing the loss of electrical signals and increasing the speed of impulse transmission. The action potential "jumps" from one node of Ranvier (the small gaps between myelin sheaths) to the next, a process known as saltatory conduction. This allows for faster transmission of the electrical signal.

Unmyelinated Nerve Fibers: In unmyelinated neurons, the axon lacks a myelin sheath. The action potential propagates continuously along the entire length of the axon. However, the speed of impulse transmission is slower compared to myelinated neurons due to the absence of saltatory conduction.